The present invention generally relates to a copying machine and, more particularly, to an electrophotographic copying machine of slit exposure type having a plurality of sequence modes of operation.
With recent advancement in integrated circuit technology, low-cost and versatile micro-computers have largely been developed and some of them are currently employed in machines for use in promotion of the public welfare. This trend applies even in the field of copying machine and, in reality, a diversity of copying machines are currently available and/or suggested.
Of the copying machines now available in the commercial market, a copying machine utilizing a micro-computer, especially a computerized electrophotographic copying machine of either slit exposure type or powder image transfer type which had generally been considered complicated in sequence of control, has now been developed to such an extent that a variety of functions can automatically be controlled accurately and efficiently in sequence. This type of computerized, or computer-controlled, copying machine involves numerous advantages.
On the other hand, diversification of the available functions has posed numerous problems. In other words, the programmed sequence control performed by a micro-computer is the sequence control wherein desired control signals are generated when counted values of clock pulses which are generated in the micro-computer and which have been counted and/or divided to attain programmed numerical data each determined for a particular control objective, the programmed numerical data being, however, correlated to each other as a whole so that the control objectives can be controlled in a predetermined sequence. In view of this, where the sequence control by the digital timer is desired to be performed in exact and accurate unison with operation of the machine with respect to the whole control objectives, not only are timers of different preset times one for each of the control objectives required, but also the number thereof is many.
In an electrophotographic copying machine, where it is desired to have a number of functional capabilities of, for example, reproducing an image in one of a plurality of magnifications and on a copying paper of a size selected from a plurality of sizes of papers with which the machine can work, and yet, where those functional capabilities are required to be controlled in sequence, not only is the available combination thereof many, but also a corresponding number of timers are required. In addition thereto, a difficulty is involved in carrying out a check as to whether or not the sequence control being performed ensures an exact and correct operation of the copying machine. Especially, where repeated reproduction of the same image on two or more copying papers is to be carried out, this should not be a mere repetition of the sequence that is performed during the reproduction of an image on one copying paper and, in order to increase the copying speed, measures must be taken to enable the machine to be ready for the next succeeding reproduction of the image half-way during the sequence for the preceding reproduction of the image being currently performed. Heretofore, in order for the next succeeding copying operation, specifically the scanning of the image to be reproduced, to be initiated during the repeated copying operation of the machine, a complete return of the optical scanner to the original position after having been moved to the opposite, scanned position has generally been required and so is evidenced by the fact that a timing signal generated upon the complete return of the optical scanner to the original position has long been utilized.
However, with the diversification of the sequence modes, it has been found the timing at which the optical scanner returns to the original position is too early to provide a starting point at which the next succeeding copying operation is initiated in view of the position of a copying paper being supplied and also the operation of a paper jamming detector. In order to eliminate this inconvenience, it may be possible to use a timer of a preset time long enough to provide a delay before the start of the next succeeding copying operation so that the machine can be programmed so as to initiate the next succeeding copying operation after the lapse of the preset time of the timer. However, where the timer of the type referred to above is actually employed, the stand-by time during which the machine is held standstill is unnecessarily prolonged, resulting in a relatively large loss of time and also hampering the high speed operation of the copying machine.
Although the use of a timer for multi-copying for each sequence mode can be contemplated to eliminate the above described disadvantages, this in turn results in the increased number of timers employed. Yet, in the case where the timer for multi-copying is set at the mode at which the next succeeding copying operation can be initiated immediately after the complete return of the optical scanner to the original position, it is in practice difficult to coincide the timing at which the timing signal is to be generated from the timer with the timing at which the optical scanner completes its return movement to the original position. Even in this case, the timer must have a sufficiently long preset time and a loss of time is involved accordingly.